The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to a disk drive base of the HDA. The HDA includes at least one disk (such as a magnetic disk, magneto-optical disk, or optical disk), a spindle motor for rotating the disk, and a head stack assembly (HSA). The HSA includes at least one head, typically several, for reading and writing data from and to the disk. In an optical disk drive, the head will typically include a mirror and objective lens for reflecting and focusing a laser beam on to a surface of the disk. The HSA is controllably positioned in response to servo control signals from a disk controller on the PCBA. In so doing, the attached heads are moved relative to concentric circular tracks of information recorded on the disk. The spindle motor typically includes a rotatable spindle motor hub on which the disks are mounted and a stator. Rotation of the spindle motor hub results in rotation of the attached disks.
The HSA includes an actuator, at least one head gimbal assembly (HGA), and a flex cable. A conventional “rotary” or “swing-type” actuator typically includes an actuator body. The actuator body has a pivot bearing cartridge to facilitate rotational movement of the actuator. One or more actuator arms extend from the actuator body. Each actuator arm typically supports at least one HGA that includes a head. An actuator coil is supported by the actuator body opposite the actuator arms. The actuator coil is typically configured to interact with one or more magnets, typically a pair of identical magnets, to form a voice coil motor. The PCBA controls current passing through the actuator coil that results in a torque being applied to the actuator.
A latching mechanism is provided to facilitate latching of the actuator in a parked position when the heads are not being used to read from or write to the tracks of information on the disk. In the parked position, the actuator is positioned with the heads either at an inner diameter (ID) of the disk or at or beyond an outer diameter (OD) of the disk such as upon a ramp. A crash stop coupled to the disk drive base is provided to limit rotation of the actuator in a given direction. The crash stop is configured to contact a portion of the actuator when the actuator is rotated to an extreme rotational position in a given rotational direction. Another crash stop may be provided to limit actuator rotation in an opposite rotational direction. The latching mechanism may additionally function as one of the crash stops.
Disk drives have found ever increasing utility in small mobile electronic devices such as laptop and hand-held computing devices, audio devices, audio/video devices, and personal electronic organizers. In such applications there is an enhanced risk that the disk drive may be subject to mechanical shock events, for example when the host device is dropped. During a mechanical shock event, the disk drive base may experience significant rotational accelerations that can cause a sudden relative rotation of the actuator. Such a sudden relative rotation of the actuator may result in damage to the HSA, especially to its attached head gimbal assemblies. The adjacent disk surface(s) may also be damaged, which may result in loss of data. Various latch designs have attempted to secure the actuator during such mechanical shock events.
Such actuator latches may be biased (e.g. to an open position during disk drive operation) by a magnetic force during disk drive operation. For example, an actuator latch may include a ferromagnetic material (e.g. a steel ball) that is attracted to one or both voice coil motor (VCM) magnets. However, expected possible mechanical shocks during disk drive operation, especially in disk drives used in mobile electronic devices such as laptops, may require that the magnetic biasing force on the latch be increased relative to today's state of the art. Accordingly, there is need in the art for improved structures to magnetically bias an actuator latch in a disk drive.